As people’s living standards continue to improve, we are paying more and more attention to the aesthetics of the teeth. For this reason, parents who bring their children to the dental hospital to request orthodontic treatment are also increasing year by year. When the doctor proposes a treatment plan after examination, most parents are puzzled by the need to extract some good teeth for orthodontic treatment, why is this? In order to correct the crooked and misaligned teeth, doctors have to pull out the extra teeth because it occupies the normal position and affects the normal alignment of teeth; the retained baby teeth also have to be pulled out because the baby teeth do not recede will prevent the eruption of permanent teeth, resulting in malposition of permanent teeth, these situations are understandable. However, few people know that in order to straighten teeth, several teeth in normal position and healthy are also extracted if necessary, which is a special treatment for crowding and protrusion, called reduction therapy. In children with crowding and protrusion, the underlying cause is an underdeveloped dental bed or a disparity between the size of the teeth and the length of the dental bed. A small underdeveloped dental bed to accommodate the normal number and size of teeth will inevitably result in crowded teeth, a situation that cannot be effectively treated with the usual orthodontic methods, except for the extraction of one to two teeth from the dental bed, and through their sacrifice in exchange for a little precious space, allowing the other teeth to be neatly aligned. Clinically, in order to correct the crowding and protrusion of the front teeth, doctors most often remove the first premolar, that is, the tooth behind the “tiger teeth”, because this tooth, compared with other teeth, chewing function is small, after the extraction does not affect the function and aesthetics. If some children’s cuspids are crowded to the outside of the bed, the doctor does not hesitate to pull out the first bicuspids behind the cuspids, so that the cuspids slowly move to the vacant position, so that after the correction is completed, the teeth can be neat and beautiful, and can make the bite and chewing function well, in addition, the doctor sometimes also extracts the mandibular incisors to correct the crowded mandibular anterior teeth deformity. It must be pointed out that the clinical application of decreasing the number of orthodontic malformations, treatment before the doctor are after careful research and analysis, that the amount of teeth than the amount of bone is too large, with the expansion of the dental arch, moderate reduction in tooth width (i.e., reduce the diameter) and other methods are not effective before using the decreasing number of extraction method of correction, and thus the correction effect is good, both time-saving and no side effects, is a good and effective method of correction. For severely crowded teeth, some moderately crowded teeth, bruxism, maxillary protrusion, partial retrusion, severe midline misalignment and patients with high midline requirements, if not extracted will also lead to relapse due to the highly unstable treatment effect. In addition, extraction can make these malocclusions more stable and prevent recurrence. Orthodontic extractions are generally done symmetrically, the most common being the extraction of the upper, lower, left and right first premolar teeth, but there are also special cases of asymmetrical extractions. Multiple teeth, malocclusion, and caries with large defects that affect orthodontics and aesthetics should also be considered for extraction. If the third molar is present when pushing the teeth backward, the extraction of the third molar should be considered.